The present invention relates to a semiconductor device and a method for fabrication thereof having a field oxide of the buried inverse T-type suited to sub-micron MOS devices.
FIG. 1 shows a cross-sectional view of a semiconductor device where a field oxide is formed using a conventional LOCOS process (Local Oxidation of Silicon).
In the prior art, when MOS devices are fabricated, the field oxide is formed using the conventional LOCOS to isolate devices.
Thus, as shown in FIG. 1, a field oxide layer 2 is grown on a field region of a Si substrate 1 using a nitride layer (not shown herein) and a gate 3 is formed at a predetermined region, and then predetermined impurities are implanted on both sides of gate 3 to form the source and drain regions 4.
Furthermore, because, when the field oxide 2 is grown, it penetrates only a little within Si substrate 1, predetermined impurities are implanted in a field region to form a channel stop for insulation transistors.
However, the conventional fabrication process for forming the field oxide has disadvantages in that the effective area of the device is decreased, because of the generation of the bird beak and the capacitance is increased due to the pn junction. Furthermore, leakage current is generated by the damage of the edge portion, so that it is not able to completely insulate the device.